From DE 30 34 118 A1 a method is known for electronically operating and monitoring the opening and closing cycle of electrically operated assemblies, such as window lifters and electric sun roofs in motor vehicles. The path covered during opening of the assembly is electronically captured. During closing of the assembly, the captured opening path is compared electronically with the closing path which has been covered. The opening and closing path of the assembly is, for this purpose, divided up into three areas of which the first area runs from half opened to fully opened, the second area runs from half opened to practically fully closed and the third area runs from practically fully closed to completely closed.
In the first and third areas, the blocked state, which represents the fully opened and fully closed assembly, is detected and a setting member of the assembly is switched off. In the second area, the speed of a servo drive of the assembly is detected and, in the event of a reduction in the speed, the servo drive is switched off.
With this known method for producing a so-called "antijam protection," the servo drive is designed with regard to its power so that the mechanical resistances which are conditioned by the type of assembly and through outside influences are overcome over the entire displacement area. For this reason, the servo drive is designed with its power output significantly greater than is necessary for most of the displacement range. This in turn has the result that a part of the body present in the displacement area is jammed with a very high force by the assembly part which is being displaced.
A further drawback with this known method is that in the third area, that is as the window pane or sliding roof enters into the seal area for completely closing the window or roof, only the blocking state and not, however, an anti-jam state is detected.
From DE 195 07 137 A1, a method is known for monitoring and controlling the opening and closing process of electrically operated assemblies provided in motor vehicles. The power of the servo motor is controlled so that the displacement speed of the setting member is adjustable over its displacement path, in dependence on predetermined positions of the assembly. In this way, the force exerted in the jamming state by the assembly part, which is to be displaced, is to be restricted to a minimum over critical areas of the displacement path, so that the critical area is covered more slowly and thus more sensitively.
This method does indeed allow a "soft inlet" into the seal area, that is a slow displacement speed of the assembly part being displaced in the area of the seal inlet, in order to meet the requirements which are specific to individual countries with regard to an effective anti-jam protection. The slow inlet of the assembly part being displaced into the seal area, however, makes it difficult to almost impossible to recognize a standardized 4 mm round tube to determine the efficiency of the anti-jam protection and to safely distinguish the influences of the displacement forces in the sealing area. This is particularly true in the case of frameless doors and doors with panes on the outside. Furthermore, the known method leads to faulty releases of the anti-jam protection with subsequent reversing of the assembly being displaced during entry into the seal. Furthermore, the closing time of the window is increased.
From DE 35 32 078 C2, a control method is known for controlling the drive of windows or doors with an electric motor. A drive current is measured during the closing movement and the change in power is checked at constant time intervals by setting a current change boundary value. To this end, a minimum current value is predetermined inside a constant period, to which is added a fixed amount and the total sum is set or laid down as the reference value for detecting an abnormal motor load. If this boundary value is exceeded, then the closing movement is switched over to an opening movement.
The drawback with this known control method is that likewise temporary disturbances during a closing movement, which are traced back to external influences or temporary heavy going (operational difficulties) of the system, but without a jamming state existing, are substantially not recognized and lead to an opening movement although the closing movement could be continued.
From DE 41 12 998 A1, a method is known for controlling a gate drive which has a setting device, a drive device connected with the setting device, as well as a control and evaluator electronics for evaluating measuring signals and for producing control commands. To displace a gate operated by means of the gate drive, a displacement force is applied the amount of which is selected in dependence on the displacement path.
Should the displacement force exceed a predetermined safety limit, then the drive device is switched off or the drive device is reversed. This safety limit is formed by the sum of the displacement force dependent on the displacement path and a constant additional force. In this way, it is possible to compensate for interference by environmental or seasonal factors, without resulting in a premature safety cut-off.
With this known method, interference through environmental or seasonal factors are indeed taken into consideration, but the drive device is switched off every time the safety limit is exceeded. Also, here only a temporary disruption, during a closing movement which is due to outside influences or temporary difficulties in the system without a jamming case existing, is not recognized. This leads to a cut-off or reversion, although the closing movement could be continued.